【作者】 王锋；

【导师】 李东升； 杨德仁； 阙端麟；

【作者基本信息】 浙江大学 ， 材料物理与化学， 2014， 博士

【摘要】 硅基光互连技术是指利用现行成熟的互补金属氧化物半导体(CMOS)工艺研制硅基光子器件,代替电子器件实现信息的高速传输。而高效硅基光源的制备是硅基光互连应用中的难点之一,其中,氮化硅薄膜由于其优异的发光性能,成为了制备硅基光源的备选材料之一。然而,氮化硅薄膜基器件的电致发光效率依然较低,为此,人们在改善氮化硅薄膜基电致发光器件效率上做了大量的努力。本文通过在氮化硅薄膜基器件中引入银纳米颗粒实现了器件电致发光效率的提升,同时对器件电致发光的来源问题进行了详细的研讨,并在此基础上实现了器件电致发光波长的调制。本文的主要创新结果如下：(1)解决了氮化硅薄膜基器件电致发光的来源问题。通过对氮化硅薄膜基器件电致发光峰位以及不同注入电流/电压下器件的载流子输运机制的变化的详细研究,解决了氮化硅薄膜基器件两个电致发光峰的来源问题。其中,短波长的峰(P1峰)来源于陷阱在K中心的电子和位于=N-带尾态上的空穴之间的复合,而长波长的峰(P2峰)则来源于位于导带带尾态的电子和局域在≡SiO中心的空穴之间的复合。(2)提出了氮化硅薄膜基质中激子与局域表面等离子体(LSPs)之间的耦合模型,并详细研究了Purcell因子与银纳米颗粒尺寸、氮化硅薄膜基质中激子的能量以及激子与LSPs之间的距离等参数之间的关系。并且在确定这些参数之间关系的基础下,进一步通过上述耦合模型计算获得了氮化硅薄膜中激子的平均位置。(3)通过银纳米颗粒尺寸的优化,实现了氮化硅薄膜基器件电致发光效率近一个数量级的提升。通过对影响器件外量子效率的因素的分析,确定其电致发光效率的提升主要源自器件光抽取效率的提升。对于银纳米颗粒置于氮化硅薄膜上面的结构器件,光抽取效率的提升主要源自器件ITO电极的表面粗糙化。而对于银纳米颗粒置于氮化硅薄膜下面的结构器件,由局域表面等离子体共振引起的背散射的增强对光抽取效率的提升也有一定贡献。同时,内量子效率的提高和载流子注入效率的改善也对器件电致发光效率的提升有一定的贡献。(4)提出了一种研究引起器件效率衰减现象主要原因的方法。在参比样器件中我们观察到了电致发光效率衰减的现象,而对氮化硅薄膜进行高温长时间热处理或加入银纳米颗粒的器件中,这一效率衰减现象得到了有效较小。我们通过对产生光功率主导过程的分析(Z因子的确定),确定了引起这一效率衰减现象的主要原因是Auger非辐射复合过程,而载流子过注入对这一效率衰减作用甚微。(5)通过银纳米颗粒尺寸以及注入电流/电压的调节实现了氮化硅薄膜基器件电致发光波长的调制,并确定了引起器件电致发光波长移动以及P1、P2峰相对强度变化的主要原因。通过对银纳米颗粒周围增强的局域电场强度进行计算,确定了引起P1峰和P2峰峰位和强度随银纳米颗粒尺寸变化的主要原因为银纳米颗粒周围增强的局域电场强度随银纳米颗粒尺寸的变化。此外,注入电流对电致发光波长也有一定的调制作用,但效果没有银纳米颗粒尺寸的调节显著。更多还原

【Abstract】 Silicon opto-interconnection referred to the replacement of electronic devices by silicon photonic devices using existing complementary metal-oxide semiconductor (CMOS) techniques can achieve the higher transmission of information. One of the application difficulties of the silicon opto-interconnection is the fabrication of silicon-based light source with high efficiency, which is also the hotspot of the current research. Silicon nitride film is one of the candidate materials for the silicon-based light source due to its promising luminescence properties, and has attracted an extensive research interest in recent years. However, the external quantum efficiency of silicon nitride based light-emitting devices (SiNx-based LEDs) is still low, which prevent it from being used as the silicon-based light sources. Consequently, much effort have been made on improving the electroluminescence (EL) performance of SiNx-based LEDs.In this thesis, the EL efficiency of SiNx-based LEDs is improved by introducing a silver nanostructures layer into the device structure. Meanwhile, the origin of the EL of SiNx-based LEDs is discussed systematically, from which the tailoring of its EL wavelength is achieved. The primary achievement of this work is described as follow:(1) The origin of the EL of SiNx-based LEDs is discussed systematically by the evolution of the EL peaks and carrier transport mechanism on the injected current/voltage, and the band diagram is also provided. Two EL peaks (P1and P2) together with their blue-shift have been observed in our SiNx-based LEDs. We attribute the peak with shorter wavelength to the recombination of the electrons confined at the K center and the holes located at the band tail formed by=N-. While, the one with longer wavelength is originated from the recombination of the electrons located at conduction band tail and the holes confined in the center of-Si0.(2) A possible coupling mechanism between the localized surface plasmons and excitons in silicon nitride is provided. And the relationship between the Purcell factor and the deposition parameters is investigated in detail, including the average diameter of silver nanostructures, the distance between the metal nanostructures, and the emission wavelength of the luminescence matrix. Finally, the average position of excitons in the silicon nitride is estimated based on the determination of the above relationships. (3) An almost one order of magnitude enhancement of EL efficiency is achieved by the optimization of the sizes of silver nanostrutcures, which is mainly originated from the improvement of the light extraction efficiency (LEE) by the addition of silver nanostructures. For the devices with silver nanostructures onto the silicon nitride, this improved LEE is originated from the surface roughening of ITO electrode by the addition of silver nanostrutcuers. And for the devices with silver nanostructures underneath the silicon nitride, the increased back-scattering by localized surface plasmon resonance also contributes to the improved LEE. Meanwhile, the improvements of internal quantum efficiency and carrier injection efficiency also have an instructive contribution to the improved external quantum efficiency.(4) A possible method on the determination of the main origin of the efficiency droop phenomenon is provided. This phenomenon can be observed in our reference devices, which can be reduced significantly by high-temperature thermal annealing process and/or the addition of silver nanostructures. From the identification of the dominant process contributing to the output power of light as well as the carrier injection conditions for the devices with and without Ag nanostructures, we attributed this phenomenon mainly to the nonradiative Auger recombination. And the overflow of carriers has a negligible contribution on this phenomenon.(5) The tailoring of the EL wavelength of SiNx-based LEDs is achieved by the modulation of the silver nanostructure sizes and/or the injected current/applied voltage. Meanwhile, the wavelength shift of EL peaks and the relative intensity changes of P1peak and P2peak is originated from the weakned localized electrical fields surrounding silver nanostrutuctrues with the increase of silver nanostrutcures. Moreover, the modulation of EL peaks by the size of silver nanoparticles is much more significant than that by injected current.更多还原